Genetic factors underlying leukocyte telomere length (LTL) may provide insights into telomere homeostasis, with direct links to disease susceptibility. Genetic evaluation of 23,096 Singaporean Chinese samples identifies 10 genome-wide loci ( P < 5 × 10 −8 ). Several of these contain candidate genes ( TINF2 , PARP1 , TERF1 , ATM and POT1 ) with potential roles in telomere biology and DNA repair mechanisms. Meta-analyses with additional 37,505 European individuals reveals six more genome-wide loci, including associations at MPHOSPH6 , NKX2-3 and TYMS . We demonstrate that longer LTL associates with protection against respiratory disease mortality [HR = 0.854(0.804–0.906), P = 1.88 × 10 −7 ] in the Singaporean Chinese samples. We further show that the LTL reducing SNP rs7253490 associates with respiratory infections ( P = 7.44 × 10 −4 ) although this effect may not be strongly mediated through LTL. Our data expands on the genetic basis of LTL and may indicate on a potential role of LTL in immune competence.

IntroductionTelomere length, a marker for biological aging, is implicated with diabetic kidney disease (DKD); however, the association between telomere length and albuminuria progression among Asian patients with type 2 diabetes (T2D) is not well understood. Here, we aim to study whether leukocyte telomere length (LTL) may independently predict albuminuria progression in patients with T2D with preserved renal filtration function (estimated GFR >60 ml/min per 1.73 m2 and urine albumin-to-creatinine ratio [uACR] <300 mg/g).MethodsThe baseline LTL was measured by real-time polymerase chain reaction in the SMART2D cohort (n = 691) with a median follow-up of 3 years. Albuminuria progression was defined as a change in albuminuria category to a higher category and at least 30% increase in uACR from baseline in 3 years.ResultsProgressors (n = 123) had significantly shorter median LTL compared with nonprogressors (n = 568) (0.58 [0.38–0.79] vs. 0.62 [0.45–0.88], P = 0.039). Compared with subjects with longer LTL (fourth quartile), subjects with shorter LTL (first quartile) had 1.93-fold (1.04–3.60, P = 0.038) increased risk for albuminuria progression after adjustment for traditional risk factors. The association of LTL with microalbuminuria to macroalbuminuria progression was stronger than its association with normoalbuminuria to microalbuminuria (odds ratio [OR]: 1.54; 95% confidence interval [CI]: 1.02–2.32; P = 0.042 vs. OR: 1.13; 95% CI: 0.91–1.40; P = 0.263 per 1-SD decrement in natural log-transformed LTL).ConclusionTherefore, our results demonstrated that in patients with T2D with preserved renal filtration function, LTL predicts albuminuria progression beyond traditional risk factors, suggesting LTL may be novel biomarker for DKD progression.

Background Chronic kidney disease (CKD) is common among type 2 diabetes (T2D) and increases the risk of kidney failure and cardiovascular diseases. Shorter leukocyte telomere length is associated with CKD in patients with T2D. We previously reported single nucleotide polymorphisms (SNPs) associated with leukocyte telomere length in Asian population. In this study, we elucidated the association of these SNPs with CKD in patients with T2D using Mendelian randomization (MR) approach. Methods The cross-sectional association of 16 leukocyte telomere length SNPs with CKD, defined as an estimated glomerular filtration rate of less than 60 ml/min/1.73m2 was assessed among 4,768 (1,628 cases, 3,140 controls) participants in the Singapore Study of Macro-angiopathy and Micro-vascular Reactivity in Type 2 Diabetes and Diabetic Nephropathy cohorts. MR analysis was performed using the random-effect inverse-variance weighted (IVW) method, the weighted median, MR-Egger and Radial MR adjusted for age and sex-stratified by cohorts and ethnicity (Chinese and Malays), then meta-analysed. Results Genetically determined shorter leukocyte telomere length was associated with increased risk of CKD in patients with T2D (meta-IVW adjusted odds ratio = 1.51 [95% confidence interval, 1.12 - 2.12; P = 0.007; Phet= 0.547]). Similar results were obtained following sensitivity analysis. MR-Egger analysis (intercept) suggested no evidence of horizontal pleiotropy (β  =  0.010, P = 0.751). Conclusions Our findings suggest that genetically determined leukocyte telomere length is associated with CKD in patients with T2D. Further studies are warranted to elucidate the causal role of telomere length in CKD progression.

Urine haptoglobin (uHP) level prospectively predicts diabetic kidney disease (DKD) progression. Here, we aim to identify genetic determinants of uHP level and evaluate association with renal function in East Asians (EA) with type 2 diabetes (T2D). Genome-wide association study (GWAS) among 805 [236 Chinese (discovery) and 569 (57 Malay and 512 Chinese) (validation)] found that rs75444904/kgp16506790 variant was robustly associated with uHP level (MetaP = 1.21 × 10−60). rs75444904 correlates well with plasma HP protein levels and multimerization in EA but was not in perfect LD (r2 = 0.911 in Chinese, r2 = 0.536 in Malay) and is monomorphic in Europeans (1000 G data). Conditional probability analysis indicated weakening of effects but residual significant associations between rs75444904 and uHP when adjusted on HP structural variant (MetaP = 8.22 × 10−7). The rs75444904 variant was associated with DKD progression (OR = 1.77, P = 0.014) independent of traditional risk factors. In an additional validation-cohort of EA (410 end-stage renal disease (ESRD) cases and 1308 controls), rs75444904 was associated with ESRD (OR = 1.22, P = 0.036). Furthermore, increased risk of DKD progression (OR = 2.09, P = 0.007) with elevated uHP level through Mendelian randomisation analysis provide support for potential causal role of uHP in DKD progression in EA. However, further replication of our findings in larger study populations is warranted.

The role of low frequency variants associated with telomere length homeostasis in chronic diseases and mortalities is relatively understudied in the East-Asian population. Here we evaluated low frequency variants, including 1,915,154 Asian specific variants, for leukocyte telomere length (LTL) associations among 25,533 Singapore Chinese samples. Three East Asian specific variants in/near POT1, TERF1 and STN1 genes are associated with LTL (Meta-analysis P 2.49×10−14–6.94×10−10). Rs79314063, a missense variant (p.Asp410His) at POT1, shows effect 5.3 fold higher and independent of a previous common index SNP. TERF1 (rs79617270) and STN1 (rs139620151) are linked to LTL-associated common index SNPs at these loci. Rs79617270 is associated with cancer mortality [HR95%CI = 1.544 (1.173, 2.032), PAdj = 0.018] and 4.76% of the association between the rs79617270 and colon cancer is mediated through LTL. Overall, genetically determined LTL is particularly associated with lung adenocarcinoma [HR95%CI = 1.123 (1.051, 1.201), Padj = 0.007]. Ethnicity-specific low frequency variants may affect LTL homeostasis and associate with certain cancers.